A Bluetooth system provides a communication channel between two electronic devices via a short-range radio link. In particular, the Bluetooth system operates in the radio frequency range around 2.45 GHz in the unlicensed Industrial-Scientific-Medical (ISM) band. The Bluetooth radio link is intended to be a cable replacement between portable and/or fixed electronic devices. The portable devices include mobile phones, communicators, audio headsets, laptop computers, other GEOS-based or palm OS-based devices and devices with different operating systems.
The Bluetooth operating frequency is globally available, but the permissible bandwidth of the Bluetooth band and the available RF channels may be different from one country to another. Globally, the Bluetooth operating frequency falls within the 2400 MHz to 2497 MHz range. In the U.S. and in Europe, a band of 83.7 MHz bandwidth is available, and the band is divided into 79 RF channels spaced 1 MHz apart. Bluetooth network arrangements can be either point-to-point or point-to-multipoint to provide connection links among a plurality of electronic devices. Two to eight devices can be operatively connected into a piconet, wherein, at a given period, one of the devices serves as the master while the others are the slaves. Several piconets may form a larger communications network known as a scatternet, with each piconet maintaining its independence. The baseband protocol for a Bluetooth system combines circuit and packet switching. Circuit switching can be either asynchronous or synchronous. Up to three synchronous data (logical) channels, or one synchronous and one asynchronous data channel, can be supported on one physical channel. Each synchronous channel can support a 64 Kb/s transfer rate while an asynchronous channel can transmit up to 721 Kb/s in one direction and 57.6 Kb/s in the opposite direction. If the link is symmetric, the transfer rate in the asynchronous channel can support 432.6 Kb/s. A typical Bluetooth system consists of a radio link, a link control unit and a support unit for link management and host terminal interface functions. The Bluetooth link controller carries out the baseband protocols and other low-level routines. Link layer messages for link set-up and control are defined in the Link Manager Protocol (LMP). In order to overcome the problems of radio noise interference and signal fading, frequency hopping is currently used to make the connections robust.
Currently, each of the 79 RF channels is utilized by a pseudo-random hopping sequence through the Bluetooth bandwidth. The hopping sequence is unique for each piconet and is determined by the Bluetooth device address of the master whose clock is used to determine the phase of the hopping sequence. The channel is divided into time slots of 625 μs in length and numbered according to the master clock, wherein each time slot corresponds to an RF hop frequency, and wherein each consecutive hop corresponds to a different RF hop frequency. The nominal hop rate is 1600 hops/s. All Bluetooth devices participating in the piconet are time and hop synchronized to the channel. The slot numbering ranges from 0 to 227 −1 and is cyclic with a cycle length of 227. In the time slots, master and slave devices can transmit packets. Packets transmitted by the master or the slave device may extend up to five time slots. The RF hop frequency remains fixed for the duration of packet transmission.
When one Bluetooth device communicates with another Bluetooth device, one is a sending device and the other is a recipient device. There is a need to identify the sending device when pairing the sending device with the recipient device. This is necessary because, without such identification and paring, it is possible that a sending device in one's home may be accidentally connected to a recipient device of a next door neighbor, which can be just behind one of the home's walls. If the sending device is used to send images to a Bluetooth image viewer, for example, it is undesirable that the images accidentally appear on the neighbor's screen.
In general, when an end-user wishes to establish communication between a sending Bluetooth device and a recipient Bluetooth device, the user must key in the identity of the recipient device to the sending device. In the example illustrated above, the communication between the image sender and the image viewer can only be established after the end-user keys in the identification code of his or her own image viewer to the image sending device. Because each image viewer has its unique identification code, it is highly unlikely that the end-user accidentally sends his or her images to the neighbor's image viewer. The sending device in the above example can be a mobile phone and the image viewer can be a TV Dongle.
In a household that has a number of Bluetooth devices, the end-user of the devices must know the identification code for each of the devices that can or will be used as recipients. The identification code can be the last N digits of the serial number of the Bluetooth device, for example. For practical reasons, the serial number may be on a label in the battery compartment, or on a label on the bottom of a device. In order to find out the serial number, the end-user may have to take out the batteries from the battery compartment or to flip over a heavy device.
It is thus advantageous and desirable to provide a method and device for revealing the identification code of a Bluetooth device whenever the end-user wants to access it, without requiring the end-user to memorize the identification code or to go through a number of unnecessary steps to find such code.